The objectives of this proposal are to determine the structures of the biosynthetic precursors of somatostatin and glucagon using recombinant DNA technology, to elucidate the effects of neurotransmitters, hormones, and tissue growth factors on gene expression in somatostatinergic neurons, and to explore the organization of the somatostatin and glucagon genes. To these ends, complementary DNA (cDNA) corresponding to each of the major cell-free translation products of mRNA isolated from anglerfish islets has been constructed and cloned. cDNA coding for precursors of somatostatin and glucagon will be sequenced and from the DNA sequence, the amino acid sequence of the precursors will be deduced. Cloned cDNA probes will be used in hybridization assays to examine somatostatin production in non-islet tissue (brain and other peripheral tissues) and to quantitate pre-somatostatin mRNA levels in brain cell cultures as influenced by factors known to regulate neuronal growth and differentiation. cDNA probes will also be used to determine the structure of the somatostatin and glucagon genes.